Ventilation System for Tunnel Section or Covered Road

ABSTRACT

Ventilation system ( 1 ) of a tunnel or covered road section ( 2 ), in which the tunnel ( 2 ) comprises at least a first tunnel tube or carriageway ( 11; 11, 12 ) with a first entrance ( 3; 3, 5 ) and a first exit ( 4; 4, 6 ) for traffic (T 1 ; T 1 , T 2 ) through the at least first tunnel tube ( 11 ), and the ventilation system ( 1 ) is equipped for: —the production of a blind flow or recirculation flow of air inside the at least first tunnel tube during use, and —the controlled discharge of air from the blind flow or recirculation flow at the entrance and/or exit of the at least first tunnel tube.

The present invention relates to a ventilation system for a tunnel section or a covered road.

Increasing traffic congestion is constantly putting more pressure on the environment from polluting substances released from vehicles.

Vehicles, because of their use of fossil fuels, produce pollutants such as nitrogen oxides and also soot particles. In addition, traffic also produces particulates from products released through wear of the brakes and tyres of vehicles.

There are statutory regulations which provide standards for the maximum permitted exposure of the environment to the abovementioned pollutants caused by traffic, so that environmental pollution can be limited to some extent.

The release of pollutants is at its peak particularly during rush hours (peak loads of the section) when a very large number of vehicles are using the road.

A problem can occur at the mouths of tunnels and covered road sections, where the pollutants can accumulate inside the tunnel because of the reduced discharge to the environment, and such pollutants can be present in high concentrations at the mouths. There are ventilation systems which create a constant air flow in the tunnel in order to freshen the air and discharge the pollutants present in the tunnel to the environment at the entrance and/or exit or at an air outlet point.

An outflow of polluted air can then occur at the entrances and exits of the tunnel or at the air outlet point, so that the abovementioned standards can be seriously exceeded, in particular during peak loads of the tunnel.

It is an object of the present invention to provide a ventilation system for a tunnel which prevents the occurrence of peak loads of pollutants.

This object is achieved by a ventilation system of the abovementioned type for a tunnel or covered road section, in which the tunnel comprises a first tunnel tube or carriageway with a first entrance and a first exit for traffic through the first tunnel tube, and the ventilation system is equipped for:

the production of a blind flow or recirculation flow of air inside the at least first tunnel tube during use, and

the controlled discharge of air from the blind flow or recirculation flow at the entrance and/or exit of the at least first tunnel tube.

The ventilation system according to the present invention advantageously by means of the blind flow or recirculation flow ensures that the outflow of pollutants occurs in a controlled manner, so that the exposure and/or load at the ends of the tunnel tube(s) remains below the standard also during peak load of the tunnel.

The invention will be explained in greater detail below with reference to a number of drawings, in which exemplary embodiments are illustrated. They are intended only for illustrative purposes and not to limit the idea of the invention which is defined by the claims.

FIG. 1 shows diagrammatically a first embodiment of a ventilation system according to the invention;

FIG. 2 shows diagrammatically a view of a detail of the ventilation system of FIG. 1 in a further embodiment;

FIG. 3 shows diagrammatically a view of a detail of the ventilation system of FIG. 1 in yet a further embodiment;

FIG. 4 shows diagrammatically a second embodiment of a ventilation system according to the invention; and

FIG. 5 shows a view of a detail of a part of the ventilation system according to the invention.

FIG. 1 shows diagrammatically a first embodiment of a ventilation system according to the invention.

A ventilation system 1 according to the invention is installed on a tunnel or covered road section 2. The tunnel 2 comprises a first tunnel tube 11 and a second tunnel tube 12.

The first tunnel tube 11 is provided with a first entrance 3 on one side and a first exit 4 on the other side. The direction of movement of the traffic through the first tunnel tube 11 is indicated by the arrow T1.

The second tunnel tube 12 is provided with a second entrance 5 on one side and a second exit 6 on the other side. The direction of movement of the traffic through the second tunnel tube 12 is indicated by the arrow T2.

The ventilation system 1 comprises a first air barrier L1, a second air barrier L2, a third air barrier L3, and a fourth air barrier L4.

An air barrier L1, L2, L3, L4 serves to form a barrier against pollutant particles which are discharged, or tend to be discharged, from the tunnel with the traffic passing through the tunnel. Examples of an air barrier are an air curtain, or a water curtain. It is also possible to use an adaptation of one end of the tunnel by a bend in the end or an adaptation at the end of the tunnel which influences an air flow at the position of the end of the tunnel.

In one embodiment of the invention, air curtain devices are used as the air barrier. The ventilation system 1 furthermore comprises a first air pump C1, a second air pump C2, a third air pump C3, and a fourth air pump C4.

The first air curtain device L1 is placed at the first entrance 3 of the first tunnel tube 11 in order to create a first air curtain or controlled air flow, indicated by the arrow LS1, during use.

The second air curtain device L2 is placed at the first exit 4 of the first tunnel tube 11 in order to create a second air curtain or controlled air flow, indicated by the arrow LS2, during use.

The third air curtain device L3 is placed at the second entrance 5 of the second tunnel tube 12 in order to create a third air curtain or controlled air flow, indicated by the arrow LS3, during use.

The fourth air curtain device L4 is placed at the second exit 6 of the second tunnel tube 12 in order to create a fourth air curtain or controlled air flow, indicated by the arrow LS4, during use.

The direction of the arrow LS1, LS2, LS3, LS4 of the first, second, third and fourth air curtain respectively indicates the direction of flow of the air flow in the respective air curtain.

At the first exit 4 of the first tunnel tube 11, the second air curtain LS2 is maintained during operation by the first air pump C1. The first air pump C1 takes in air at a location inside the first tunnel tube 11 and conveys said air to the second air curtain device L2. A first filter F1 may possibly be accommodated in the supply line of the first air pump in order to filter the air which has been taken in.

A discharge line of the second air curtain device L2 is connected to the second air pump C2, for the purpose of extracting air at the position of the discharge line of the second air curtain device L2. The second air pump C2 is connected by means of an outlet to a supply line of the third air curtain device L3, for the purpose of supplying air to the third air curtain device L3 in order to maintain the third air curtain LS3.

At the second exit 6 of the second tunnel tube 12, the fourth air curtain LS4 is maintained during operation by the third air pump C3. The third air pump C3 takes in air at a location inside the second tunnel tube 12 and conveys said air to the fourth air curtain device L4. A third filter F3 may possibly be accommodated in the supply line of the third air pump in order to filter the air which has been taken in.

A discharge line of the fourth air curtain device L4 is connected to the fourth air pump C4, for the purpose of extracting air at the position of the discharge line of the fourth air curtain device L4. The fourth air pump C4 is connected by means of an outlet to a supply line of the first air curtain device L1, for the purpose of supplying air to the first air curtain device L1 in order to maintain the first air curtain LS1.

The ventilation system 1 furthermore comprises a control unit BE and one or more sensors S1, S2, which are placed in one or both of the tunnel tubes 11, 12.

The control unit BE is connected to the first, second, third and fourth air pump C1, C2, C3, C4 in order to control said air pumps. The control unit is furthermore connected to one or more sensors S1, S2 in the tunnel 2. The one or more sensors S can be placed near or on one of the first, second, third and/or fourth air curtain devices L1, L2, L3, L4, or at a suitable location in the first and/or second tunnel tube 11, 12. The one or more sensors S1, S2 are equipped for measuring traffic intensity, or more particularly concentrations of pollutants.

The aim of the ventilation system 1 is to ensure that effectively no pollutants are released at the ends 3, 4, 5, 6 of the first and second tunnel tubes 11, 12, or that only a maximum quantity of pollutants which does not exceed the standards set (per unit of time) can be released at the ends of the tunnels.

In order to achieve this, the ventilation system according to the invention is equipped to maintain a blind flow or recirculation flow inside the tunnel tubes 11, 12 in the following manner.

The first, second, third and fourth air curtain devices L1, L2, L3, L4 during use create the first, second, third and fourth air curtain respectively which serve as barriers for the air present in the first and second tunnel tubes 11, 12 in order to ensure that effectively substantially no pollutant in the air leaves the tunnel.

At the exit side of each tunnel tube 11, 12, the pollutant will accumulate because of the entrained flow T1, T2 created by the traffic.

By means of the ventilation system according to the invention, a blind flow or recirculation flow is, however, created, so that the polluted air (with the pollutants) is kept substantially inside the tunnel tubes.

By adjusting the strength of the individual air curtains by means of the control unit BE to the traffic flow (which can be determined, for example, by means of sensors (not shown) in the road surface of each tunnel tube) and the entrained air flows caused by the traffic flow in each of the tunnel tubes, it is possible in this way to obtain a storage space for pollutants in the tunnel tubes. A blind flow is also created in this way.

By adjusting the strength of the air curtains (i.e. the air flow velocity of LS1, LS2, LS3, LS4), it is possible to obtain an effective barrier against inflow of entrained outside air and outflow of air out of the tunnel tube 11, 12, and an accumulation of pollutants can occur in the tunnel tube 11, 12.

In addition, the ventilation system can be provided in such a way that by way of the air output of one or more of the air pumps C1, C2, C3, C4 the air discharge at one or more of the air curtains is regulated in such a way that the blind flow is adapted and a controlled outflow of polluted air, or accumulated polluted air, out of the tunnel tube 11, 12 occurs. This means that the ventilation system can ensure that the standard for pollutants at the position of the ends 3, 4 of the tunnel is not exceeded. In this way, it is possible to use the tunnel as a buffer for pollutants and to allow the release of these pollutants delayed in time (for example, outside a period with peak load of the tunnel).

The control unit BE is equipped for receiving from each of the one or more sensors S1, S2 signals which are related to the concentrations of pollutants. On the basis of the concentrations measured by the one or more sensors S1, S2, the control unit BE is able to set the air output of the air pumps C1, C2, C3, C4, so that the strength of the respective corresponding air curtain can be set.

Of course, traffic moving through the tunnel tube 11, 12 will pass through the air curtains, so that the shut-off is not complete, but the strength of the air curtains can be set in such a way that the outflow of polluted air out of the tunnel tube 11, 12 is greatly reduced compared with the situation in which there are no air curtains at the ends 3, 4, 5, 6 of the tunnel.

In addition, the ventilation system 1 according to the invention can provide for air which is as a blind flow or recirculation flow to be conveyed through the first and/or second filter F1, F2 in order to remove pollutants from the air. This ensures that the concentrations of pollutants in the tunnel tube 11, 12 can likewise be controlled.

FIG. 2 shows diagrammatically a view of a detail of the ventilation system of FIG. 1 in a further embodiment.

In a further embodiment, the ventilation system can use a control system which is regulated by valves for the filter used in the suction line of the second and/or fourth air pump C2, C4. FIG. 2 shows the situation around the second air pump C2. The suction line L2 comprises a first suction branch A1 in which a first air filter F1 is accommodated, and a second suction branch A2. Both suction branches A1, A2 are in communication with the interior of the first tunnel tube 11. The first and second suction branches are provided with a first and second control valve V1, V2 respectively, which under control of the control unit BE can adjust the output through each of the suction branches A1, A2.

It will be clear to the person skilled in the art that such a device can also be constructed on the suction line of the fourth air pump C4, so that no further explanation as regards the fourth air pump is given here.

FIG. 3 shows diagrammatically a view of a detail of the ventilation system of FIG. 1 in yet a further embodiment.

In yet a further embodiment, an internal filter system can be placed on one or both tunnel tubes 11, 12 in order to extract air inside the respective tunnel tube 11, 12, and to filter said air and pump it back into the tunnel tube. This has the advantage that the accumulation of pollutants inside the tunnel tube 11 can be controlled. As an example, an internal filter system F5 is shown on the first tunnel tube 11. A fifth air pump C5 is connected by way of a supply line and by way of a discharge line to the interior of the tunnel tube 11. By way of a control valve V5 and a filter F5, during use the fifth air pump C5 takes in air out of the tunnel tube 11. After passing through the filter F5, the air has been filtered. The air pump C5 pumps the filtered air back to the interior of the tunnel tube 11.

It will be clear to the person skilled in the art that such a device can also be constructed on the second tunnel tube 12, so that no further explanation as regards the second tunnel tube 12 is given here.

The invention can also be used when a single tunnel, or tunnel tube, is being used for two-way traffic.

FIG. 4 shows diagrammatically a second embodiment of a ventilation system according to the invention. The same reference numerals as those in preceding figures refer to identical elements.

A ventilation system 1 according to the invention is installed on a tunnel or covered road section 2. The tunnel 2 comprises a first tunnel tube 11 or a first carriageway which is provided with a first entrance 3 on one side and a first exit 4 on the other side.

The ventilation system 1 comprises a first air pump C1, a second air pump C2, a first air curtain device L1, a second air curtain device L2, and at least a first filter F1.

The first air curtain device L1 is placed at the first entrance 3 of the tunnel tube 11 in order to create a first air curtain or controlled air flow, indicated by the arrow LS1, during use.

The second air curtain device L2 is placed at the first exit 4 of the tunnel tube 11 in order to create a second air curtain or controlled air flow, indicated by the arrow LS2, during use.

The direction of the arrow LS1, LS2 of the first and second air curtain respectively indicates the direction of flow of the air flow in the respective air curtain.

A discharge line of the first air curtain device L1 is connected to the first air pump C1, for the purpose of extracting air at the position of the discharge line of the first air curtain device L1. The at least first filter F1 is accommodated in a supply line of the first air pump C1, in order to filter the air which has been taken in.

Furthermore, a discharge line of the second air curtain device L2 is connected to the second air pump C2, for the purpose of extracting air at the position of the discharge line of the second air curtain device L2. The second air pump C2 is connected by means of an outlet to a supply line of the first air curtain device L1, for the purpose of supplying air to the first air curtain device L1 in order to maintain the first air curtain LS1.

Furthermore, the ventilation system 1 comprises a control unit BE and one or more sensors S.

The control unit BE is connected to the first and second air pump C1, C2, in order to control the first and second air pumps. The control unit is furthermore connected to one or more sensors S1, S2 in the tunnel 2. The one or more sensors S can be placed near or on the first curtain device L1 and/or second air curtain device L2, or at a suitable location in the tunnel tube 11. The one or more sensors S are equipped for measuring traffic intensity, or more particularly concentrations of pollutants.

The aim of the ventilation system 1 is to ensure that effectively no pollutants are released at the ends 3, 4 of the tunnel, or that only a maximum quantity of pollutants which does not exceed the standards set (per unit of time) can be released at the ends 3, 4 of the tunnel.

In order to achieve this, the ventilation system according to the invention is equipped to maintain a blind flow or recirculation flow inside the tunnel tube 11 in the following manner.

The first air curtain device L1 and second air curtain device L2 during use create the first and second air curtain, which serve as barriers for the air present in the tunnel tube 11. The blind flow can be maintained by extracting the flowing air LS1, LS2 from the air curtain at the respective discharge line at each of the two air curtain devices L1, L2, and reusing it at the other of the two air curtain devices L1, L2 in order to feed the air flow of that air curtain. By adjusting the strength of the air curtains (i.e. the air flow velocity of LS1, LS2), it is possible to obtain an effective barrier against outflow of air out of the tunnel tube 11, and an accumulation of pollutants can occur in the tunnel tube 11.

In addition, the ventilation system can be provided in such a way that by way of the air output of one or both air pumps C1, C2 the air discharge at one or both air curtains is regulated in such a way that the blind flow is adapted and a controlled outflow of (accumulated) polluted air out of the tunnel tube 11 occurs. For the regulation of the air output through an air pump, it is also possible to use regulating valves which are controlled by the control unit. This means that the ventilation system can ensure that the standard for pollutants at the position of the ends 3, 4 of the tunnel are not exceeded. In this way, it is possible to use the tunnel as a buffer for pollutants and to allow the release of these pollutants delayed in time (for example, outside a period with peak load of the tunnel).

The control unit BE is equipped for receiving from each of the one or more sensors S signals which are related to the concentrations of pollutants. On the basis of the concentrations measured by the one or more sensors S, the control unit BE is able to set the air output of the first and/or second air pump C1, C2 respectively, so that the strength of the first and second air curtain respectively can be set. Account can be taken here of the net entrained flow of air in the tunnel as a result of the traffic intensity and the predominant direction of movement of the traffic in the tunnel.

FIG. 5 shows a view of a detail of a part of the ventilation system according to a further embodiment of the invention.

It is found to be advantageous to direct the air flow of the air curtains obliquely inwards into the tunnel tube at least at the exit of a tunnel tube. This creates a flow component of the air flow which is directed in the opposite direction to the direction of movement of the traffic and the entrained flow in the tunnel. The barrier effect of the air flow at the tunnel opening is improved in this way.

FIG. 5 shows diagrammatically the second air curtain device L2 at the first exit 4 of the first tunnel tube 11. The air flow LS2 is placed at an oblique angle relative to the tunnel walls, so that a transverse flow component LS2 y and a parallel flow component LS2 x are formed. The parallel flow component LS2 x of the air flow LS2 blown in by the air pump C1 has a direction which is substantially opposite to the direction of travel of traffic T1 and entrained flow in the tunnel tube 11.

It will be clear to the person skilled in the art that such a device can also be constructed at the second exit 6 of the second tunnel tube 12, so that at the position of said exit 6 a parallel flow component LS4 x of the air flow LS4 blown in by the air pump C3 has a direction which is substantially opposite to the direction of travel of traffic T2 and the entrained flow in the tunnel tube 11.

At the first or second entrance 3, 5 of the first and second tunnel tube 11, 12 respectively, it is also possible to form a parallel flow component of LS1, LS3 respectively which flows in the same direction as that of the direction of movement of the traffic T1, T2, but in the light of what has been stated above that will now be clear to the person skilled in the art, so that no further explanation as regards the parallel flow component at the entrance(s) of the tunnel tube(s) will be given here.

It is pointed out that in addition to or instead of sensors which measure concentrations of pollutants (or a measured variable linked to them), sensors S, S1, S2 which determine, for example, the traffic intensity can also be used, in which case the traffic intensity or a derivative of traffic intensity is used as the criterion for the control of accumulation of substances in the tunnel.

Other alternatives and equivalent embodiments of the present invention are conceivable within the idea of the invention, as will be clear to the person skilled in the art. The idea of the invention is limited only by the appended claims. 

1-19. (canceled)
 20. Ventilation system (1) of a tunnel or covered road section (2), in which the tunnel (2) comprises at least a first tunnel tube (11; 11, 12) with a first entrance (3; 3, 5) and a first exit (4; 4, 6) for traffic (T1; T1, T2) through the at least first tunnel tube (11; 11, 12), in which the ventilation system (1) comprises an air barrier (L1, L2; L1, L2, L3, L4) at each end (3, 4; 3, 4, 5, 6) of the at least one tunnel tube (11; 11, 12), and in which each of the air barriers during use is capable of forming a barrier against polluting particles coming out of the tunnel, the ventilation system comprising air pumps (C1, C2; C1, C2, C3, C4) for extracting air at one barrier and supplying that air to another barrier at an other end of the at least first tunnel tube and the ventilation system (1) is equipped for: —the production of a blind flow or recirculation flow of air inside the at least first tunnel tube during use, and —the controlled discharge of air from the blind flow or recirculation flow at the entrance and/or exit of the at least first tunnel tube.
 21. Ventilation system (1) of a tunnel or covered road section (2) according to claim 20, in which the tunnel (2) comprises a first tunnel tube (11) with a first entrance (3) and a first exit (4) and a second tunnel tube (12) with a second entrance (3) and a second exit (4); in which the ventilation system (1) comprises a first air pump (C1), a second air pump (C2), a third air pump (C3), and a fourth air pump (C4), a first air curtain device (L1), a second air curtain device (L2), a third air curtain device (L3), and a fourth air curtain device (L4), in which the first air curtain device (L1) is placed at the first entrance (3) of the first tunnel tube (11) in order to create a first air curtain or controlled air flow (LS1) during use, and the second air curtain device (L2) is placed at the first exit (4) of the first tunnel tube (11) in order to create a second air curtain or controlled air flow (LS2) during use; the third air curtain device (L3) is placed at the second entrance (3) of the second tunnel tube (12) in order to create a third air curtain or controlled air flow (LS3) during use, and the fourth air curtain device (L4) is placed at the second exit (4) of the second tunnel tube (12) in order to create a fourth air curtain or controlled air flow (LS4) during use; the first air pump (C1) is connected to a supply line of the second air curtain device (L2), for the purpose of supplying air to the second air curtain device (L2) in order to maintain the second air curtain (L2); the second air pump (C2) is connected to a discharge line of the second air curtain device (L2), for the purpose of extracting air at the position of the discharge line of the second air curtain device (L2), and by way of a first further connection is connected to a supply line of the third air curtain device (L3), for the purpose of supplying air to the third air curtain device (L3) in order to maintain the third air curtain (LS3); the third air pump (C3) is connected to a supply line of the fourth air curtain device (L4), for the purpose of supplying air to the fourth air curtain device (L4) in order to maintain the fourth air curtain (LS4); the fourth air pump (C4) is connected to a discharge line of the fourth air curtain device (L4), for the purpose of extracting air at the position of the discharge line of the fourth air curtain device (L4), and by way of a second further connection is connected to a supply line of the first air curtain device (L1), for the purpose of supplying air to the first air curtain device (L1) in order to maintain the first air curtain (LS1); and the ventilation system is equipped to produce the blind flow or recirculation flow in the first and second tunnel tubes (11, 12) of the tunnel (2) by an adjustable air output of the air flow (LS1; LS2; LS3; LS4) of the first, second, third and fourth air pump (C1; C2; C3; C4) respectively.
 22. Ventilation system (1) of a tunnel or covered road section (2) according to claim 20, in which the ventilation system (1) also comprises a first air pump (C1) and a second air pump (C2); the first air barrier comprises a first air curtain device (L1), and the second air barrier comprises a second air curtain device L2 (L2); the first air curtain device (L1) is equipped for creating a first air curtain or controlled air flow (LS1) during use, and the second air curtain device (L2) is equipped for creating a second air curtain or controlled air flow (LS2) during use; the first air pump (C1) is connected to a discharge line of the first air curtain device (L1), for the purpose of extracting air at the position of the discharge line of the first air curtain device (L1), and by way of a first further connection is connected to a supply line of the second air curtain device (L2), for the purpose of supplying air to the second air curtain device (L2); the second air pump (C2) is connected to a discharge line of the second air curtain device (L2), for the purpose of extracting air at the position of the discharge line of the second air curtain device (L2), and by way of a second further connection is connected to a supply line of the first air curtain device (L1), for the purpose of supplying air to the first air curtain device (L1), and the ventilation system is equipped for producing the blind flow or recirculation flow in the tunnel tube (11) by an adjustable air output of the air flow (LS1; LS2) of the first and second air pump (C1, C2) respectively.
 23. Ventilation system (1) according to claim 21, in which the ventilation system (1) comprises a control unit (BE; BE1) and one or more sensors (S), in which the control unit is connected to each of the air pumps (C1, C2; C1, C2, C3, C4), for the purpose of controlling said air pumps, and is connected to one or more sensors in the tunnel, in which the one or more sensors are equipped for measuring a measured variable related to traffic intensity, and in which the control unit is equipped for receiving signals from the one or more sensors, and for establishing in relation to said signals what air output of the air flow (LS1, LS2; LS1, LS2, LS3, LS4) of the respective air pump (C1, C2; C1, C2, C3, C4) is set.
 24. Ventilation system (1) according to claim 23, in which the sensors (S; S1, S2) are equipped for measuring signals related to concentrations of pollutants.
 25. Ventilation system (1) according to claim 24, in which the sensors (S; S1, S2) at least are placed either at at least one air barrier (L1, L2; L1, L2, L3, L4) or inside the at least one tunnel tube (11; 11, 12).
 26. Ventilation system (1) according to claim 21, in which the ventilation system (1) comprises at least a first filter (F1), which is accommodated in a suction line of the first air pump (C1), for the purpose of filtering the air taken in during use.
 27. Ventilation system (1) according to claim 26, in which the ventilation system (1) comprises a second filter (F2), which is accommodated in a suction line of the second air pump (C2), for the purpose of filtering the air taken in during use.
 28. Ventilation system (1) according to claim 26, in which the ventilation system (1) comprises a third filter (F3), which is accommodated in a suction line of the third air pump (C3), for the purpose of filtering the air taken in during use.
 29. Ventilation system (1) according to claim 20, in which the ventilation system (1) comprises a fifth air pump (C5), which by way of a supply line and by way of a discharge line connected to the interior of the at least one tunnel tube (11; 11, 12), a filter (F5) being accommodated in the supply line of the fifth air pump (C5).
 30. Ventilation system (1) according to claim 29, in which a control valve (V5) is accommodated in the supply line, for the purpose of controlling an air output by the fifth air pump (C5.
 31. Ventilation system (1) according to claim 26, in which the filter (F1; F2; F3; F5) is equipped for filtering particulate and/or nitrogen oxide and/or carbon monoxide and/or hydrocarbons out of the air taken in.
 32. Ventilation system (1) according to claim 22, in which the control unit (BE; BE1) is equipped for adapting the recirculation flow in the tunnel (2) in order to control the outflow of air out of the tunnel (2) as a function as concentration of pollutants established by the sensors (S; S1, S2) and/or traffic intensity established by the sensors.
 33. Ventilation system (1) according to claim 32, in which the control unit (BE; BE1) is equipped for a control with a time delay, so that air from the recirculation flow flows out of the tunnel delayed in time.
 34. Ventilation system (1) according to claim 20, in which the air barrier (L2; L2, L4) on the exit side (4; 4, 6) is equipped for during use creating the corresponding air flow (LS2; LS2, LS4) with a flow component (LS2 x; LS2 x, LS4 x) of the air flow which has a direction which is substantially parallel to and in the opposite direction to a direction of travel of traffic (T1; T1; T2) in the tunnel tube (11; 11, 12).
 35. Ventilation system (1) according to claim 20, in which the air barrier (L1; L1, L3) at the entrance side (3; 3, 5) is equipped for during use creating the corresponding air flow (LS2; LS2, LS4) with a flow component of the air flow which has a direction which is substantially parallel to and in the same direction as a direction of travel of traffic (T1; T1; T2) in the tunnel tube (11; 11, 12).
 36. Ventilation system (1) according to claim 22, in which the ventilation system (1) comprises a control unit (BE; BE1) and one or more sensors (S), in which the control unit is connected to each of the air pumps (C1, C2; C1, C2, C3, C4), for the purpose of controlling said air pumps, and is connected to one or more sensors in the tunnel, in which the one or more sensors are equipped for measuring a measured variable related to traffic intensity, and in which the control unit is equipped for receiving signals from the one or more sensors, and for establishing in relation to said signals what air output of the air flow (LS1, LS2; LS1, LS2, LS3, LS4) of the respective air pump (C1, C2; C1, C2, C3, C4) is set. 